On-chip optical isolator using surface acoustic wave

A major issue in integrated optics is the protection of on-chip lasers against undesired external feedback. In non-integrated systems, undesired reflections can be easily blocked using Faraday isolators. However, Faraday isolators require magneto-optic materials, which are difficult to integrate into compact devices. Yu and Fan [1] have proposed a non-magnetic integrated isolator, in which a transverse mode of an optical waveguide is converted to another transverse mode only for a single propagation direction. However, the best implementation so far [2], based on a transversely non-uniform index modulation in a semiconductor, showed high losses. We present a novel design to achieve such a modulation in lowloss dielectric waveguides, using surface acoustic waves. We theoretically describe how to realize the two most essential features, which are a short interaction length and a wide isolation bandwidth..